The invention relates to a constant velocity universal joint having a hollow outer member with a central cavity whose inner face, in meridian planes, is provided with first and second outer running grooves. The running grooves extend along the longitudinal axis of the outer member and alternate on the circumference. An inner member is arranged in the central cavity of the outer member. The inner member has a spherical outer face which, in meridian planes, is provided with first and second inner running grooves. The grooves extend along the longitudinal axis of the inner member and are positioned opposite the respective first or second outer running grooves. Each running groove is undercut-free starting from one of the two opening end faces of the outer member and inner member. For torque transmitting purposes, each set of opposing outer and inner opposing running grooves jointly accommodate a ball which is guided radially in windows of a cage arranged between the outer face of the inner member and the inner face of the outer member.
U.S. Pat. No. 3,133,431 discloses a joint with tracks for torque transmitting balls. The tracks may optionally be undercut-free towards their two open ends. The joint is designed as a plunging joint. For a joint with a cage, the tracks extend in a straight line. For a cage-less joint, the tracks, in addition to extending at an angle in the meridian plane, are curved in a plane which extends at a right angle to the meridian plane. Only when the tracks extend in a straight line is it possible for the tracks to be undercut-free.
GB-PS 847 569 describes a fixed joint with tracks, which extend with a radius, for torque transmitting balls extending in meridian planes. The radii of the track bases of two track pairs opening in opposite directions is offset relative to the joint center. The joint has a ball guiding cage designed as a hollow spherical dish. The cage and outer part and inner part of the joint are provided with concentric spherical faces to mutually guide each other. The ball tracks and the guiding track of the cage are undercut and therefore cannot simply be produced by precision forming.
In the case of the said design principles, the forces acting on the cage are offset by the alternate openings of the tracks for the ball. However, this does not happen in all operating conditions because the contact of the balls in the tracks over the entire range of articulation angles changes, which inter alia results in a change of direction of the load applied to the cage, thus placing the cage is in an unstable condition. Joints whose tracks extend in a straight line in meridian planes are subject to a further disadvantage in that, towards one end of each track, the track depth which is decisive for the torque transmitting capacity is decreased considerably.
It is the object of the present invention to provide a joint which exhibits stable guiding conditions over the entire range of articulation angles and whose outer and inner members can be produced in a non-chip forming manner by precision forming.
This object is achieved in the present invention for both directions of rotation, over the entire range of articulation angles and in all rotational angular positions. The contact tracks of the balls in first and second outer running grooves of the inner member are traced by opposing contact points of the balls in the sets of outer and inner opposing running grooves. The contact points and center of balls define a cage control angle which is always greater than the self-inhibitions angle and greater than 7.degree..